Method of stabilizing lubricant additive compositions



United States Patent METHOD OF STABILIZING LUBRICANT ADDITIV E COMPOSITIONS Clyde S. Scanley, Gary, Ind., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application June 22, 1953, Serial No. 363,386

3 Claims. (Cl. 252-32.7)

This invention relates to a method of preparing stable lubricant additive compositions, and more particularly relates to a method of preparing stable mixtures of an oil-soluble alkali metal-containing neutralized reaction product of .a phosphorus sulfide and a hydrocarbon and a polyvalent salt of a dihydrocarbon dithiophosphate.

In order to improve the properties of hydrocarbon lubricating oils, particularly those adapted for use in internal combustion engines, it has become the practice to incorporate in such oils various types of lubricant additives, such as detergent-type additives, corrosion inhibitors, anti-oxidants, pour point depressors, extreme pressure agents, anti-foam agents, etc. Among the detergent-type additives the neutralized reaction products of a phosphorus sulfide and a hydrocarbon of the type described in U. S. Patent 2,316,082 have been successfully employed. Frequently, such reaction products are used in combination with certain corrosion inhibitors, such as polyvalent metal salts of a dihydrocarbon dithiophosphate, particularly a zinc salt of a dialkyl dithiophosphate. It has been observed that under certain conditions difficulty is encountered in obtaining stable solutions or dispersions in oil of mixtures of the salt of dihydrocarbon dithiophosphates and the alkali metal neutralized reaction products of a phosphorus sulfide and a hydrocarbon, i. e., under normal methods of incorporating such additives in the lubricating oil, the dihydrocarbon dithiophosphate salt will often separate or precipitate out of the oil composition.

It is an object of the present invention to provide a method of forming a stable mixture of an oil-soluble metal salt of a dihydrocarbon dithiophosphate and an oil-soluble alkali metal-containing neutralized reaction product of a phosphorus sulfide and a hydrocarbon in a hydrocarbon lubricating oil. Another object of the invention is to provide a method of treating a mixture of an oil-soluble zinc dialkyl dithiophosphate and an oilsoluble alkali metal-containing neutralized reaction product of a phosphorus sulfide and a hydrocarbon in a hydrocarbon lubricating oil to form a stable lubricant composition from which the zinc dialkyl dithiophosphate will not separate or precipitate out. invention is to provide a method of improving the compatibility in hydrocarbon lubricating oils of a mixture of a'metal salt of a dihydrocarbon dithiophosphate with an oil-soluble alkali metal-containing neutralized reaction product of the phosphorus'sulfide and a hydrocarbon. ..In accordance with the present invention, the above objects can be attained by heatinga mixture of an oil-- soluble metal salt .of a hydrocarbon dithiophosphate, such as a zinc dialkyl dithiophosphate, and an oil-soluble alkali metal-containing neutralized reaction product of a phosphorus sulfide and ahydrocarbon to temperatures of from about 240 F. to about 450 F., and preferably from about 250 F. to about 350 F., for a sufiicient length of time until a cooled sample of the heattreated mixture will not form a'precipitate after standingfor at least about three weeks. Usually, heating the rnixture'at Still another object of the Patented July 16, 15257 said temperatures for a period of time from about 6 hours to about one-half hour, and preferably from about 4 hours to about 2 hours, respectively, is adequate. The described mixture as such or in a hydrocarbon lubricating oil can be treated in the manner described.

The dithiophosphate used in the practice of the present invention is one having the general formula in which R is a hydrocarbon radical, such as an alkyl, cycloaliphatic or aryl radical, M is a polyvalent metal, such as for example, nickel, aluminum, cadmium, tin, zinc, magnesium, calcium, strontium, barium, etc., and n is the valence of M. Preferably, the dithiophosphate is a dialkyl dithiophosphate in which the alkyl group contains from about 5 to about 30 carbon atoms, such as for example, dibutyl dithiophosphate, diheptyl dithiophosphate, dihexyl dithiophosphate, diamyl dithiophosphate, dioctyl dithiophosphate, dilauryl dithiophosphate, dioctadecyl dithiophosphate, etc. Diaryl dithiophosphates, such as diphenyl dithiophosphate, di(2,4-diamylphenyl) dithiophosphate, etc., can also be used. Although any of the metal dihydrocarbon dithiophosphates can also be employed, the zinc dialkyl dithiophosphates in which the alkyl groups contain from about 5 to about 12 carbon atoms are preferred.

The phosphorus sulfide-hydrocarbon reaction product additive is the alkali metal-containing neutralized reaction products of a phosphorus sulfide, such as a phosphorus pentasulfide, and' a hydrocarbon of the type described in U. S. Patent 2,316,082, issued to C. M. Loane et al., April 6, 1943. As taught in this patent, the preferred hydrocarbon constituent of the reaction is a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular weight mono-olefin hydrocarbons, such as propylene, butenes, amylenes or copolymers thereof. Such polymers may be obtained by the polymerization of mono-olefins of less than 6 carbon atoms in the presence of a catalyst, such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride or other similar halide catalysts of the Friedel-Crafts type.

The polymers employed are preferably mono-olefin I polymers or mixtures of mono-olefin polymers and isomono-olefin polymers having molecular weights ranging from about 150 to about 50,000 or more, and preferably from about 500 to about 10,000. Such polymers can be obtained, for example, by the polymerization in the liquid phase of a hydrocarbon mixture containing monoand isomono-olefins, such as butylene and isobutylene at a temperature of from about F. to about F. in the presence of a metal halide catalyst of the Friedel-Crafts type, such as for example, boron fluoride, aluminum chloride, and the like. In the preparation of these polymers, a hydrocarbon mixture containing isobutylene, butylenes and butanes recovered from petroleum gases, especially those gases produced in the cracking of petroleum oils in the manufacture of gasoline can be used.

Another suitable polymer is that obtained by polymerizing in the liquid phase a hydrocarbon mixture comprising substantially C3 hydrocarbons in the presence of an aluminum chloride-complex catalyst. The catalyst is preferably prepared by heating aluminum chloride with isooctane. The hydrocarbon mixture is introduced into the bottom of the reactor and passed upwardly through the catalyst layer, while a temperature of from about 50 F. to about F. is maintained in the reactor.

The propane and other saturated gases pass through the catalyst while the propylene is polymerized under these conditions. The propylene polymer can be fractionated to any desired molecular weight, preferably from about 500 to about 1000, or higher.

Other suitable polymers are those obtained by polymerizing a hydrocarbon mixture containing about to about 25 isobutylene at a temperature of from about 0 F. to about 100 F., and preferably 0 F. to about 32 F. in the presence of boron fluoride. After the polymerization of the isobutylene, together with a relatively minor amount of the normal olefins present, the reaction mass is neutralized, washed free of acidic substances and the unreacted hydrocarbons subsequently separated from the polymers by distillation. The polymer mixture so obtained, depending upon the temperature of reaction, varies in consistency from a light liquid to viscous oily material andcontains polymers having molecular Weights ranging from about 100 to about 2000, or higher. The polymers so obtained may be used as such or the polymers may be fractionated under reduced pressure into fractions of increasing molecular weights and suitable fractions obtained reacted withthe phosphorus sulfide to obtain the desired reaction products. The bottoms resulting from the fractionation of the polymer which have Saybolt Universal viscosities at 210 F. ranging from about 50 seconds to about 10,000 seconds are well suited for this purpose.

Essentially paraftinic hydrocarbons, such as bright stock residuurns, lubricating oil distillates, petrolatums, or paraffin waxes may be used. There can also be employed the condensation products of any of the foregoing hydrocarbons, usually through first halogenating the hydrocarcarbons with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Examples of other high molecular weight olefinic hydrocarbons which can be employed are cetene (C16), cerotene (C26), melene (C30), and mixed high molecular Weight alkenes obtained by cracking petroleum oils.

Other preferred olefins suiable for the preparation of the phosphorus sulfide reaction products are olefins having at least 20 carbon atoms in the molecule of which from about 13 carbon atoms 'to about 18 carbon atoms, and preferably at least carbon atoms, are in a long chain. Such olefins can be obtained by the dehydrogenation of alkyl halides, preferably long chain alkyl halides, particularly halogenated paraffin Waxes.

As a starting material there can be used the polymer or synthetic lubricating oil obtained by polymerizing unsaturated hydrocarbons resulting from the vapor phase cracking of paraffin waxes in the presence of aluminum chloride which is fully described in U. S. Patents 1,955,- 260; 1,970,402 and 2,091,398. Still another type of olefin polymer which may be employed is the polymer resulting from the treatment of vapor phase cracked gasoline and/ or gasoline fractions with sulfuric acid or solid adsorbents, such as fullers earth, whereby unsaturated polymerized hydrocarbons are removed. The reaction products of the phosphorus sulfide and the polymers resulting from the voltolization of hydrocarbons as described, for example, in U. S. Patents 2,197,768 and 2,191,787 are also suitable.

Other hydrocarbons that can be reacted with a phosphorus sulfide are aromatic hydrocarbons, such as for example, benzene, naphthalene, toluene, xylene, diphenyl and the like or with an alkylated aromatic hydrocarbon,

such as for example, benzene having an alkyl substituent from about 200 F. to about 400 F., using from about 1% to about 50%, and preferably from about 5% to about 25% of the phosphorus sulfide in the reaction. It is advantageous to maintain a non-oxidizing atmosphere, such as for example, an atmosphere of nitrogen above the reaction mixture. Usually, it is preferable to use an amount of the phosphorus sulfide that will completely react with the hydrocarbon so that no further purification becomes necessary; however, an excess amount of phosphorus sulfide can be used and separated from the product by filtration or by dilution with a hydrocarbon solvent, such as hexane, filtering and subsequently removing the solvent by suitable means, such as by distillation. If desired, the reaction product can be further treated with steam at an elevated temperature of from about 100 F. to about 600 F.

The phosphorus sulfide-hydrocarbon reaction product normally shows a titratable acidity which is neutralized by treatment with a basic alkali metal reagent.

The neutralized phosphorus sulfide-hydrocarbon reaction product can be obtained by treating the acidic reaction product with a suitable alkali metal basic compound, such as hydroxide, carbonate oxide or sulfide of an alkali metal, such as for example, potassium hydroxide, sodium hydroxide, sodium sulfide, preferably a basic potassium compound, e. g., KOH. The neutralization of the phosphorus sulfide-hydrocarbon reaction product is carried out preferably in a non-oxidizing atmosphere by contacting the acidic reaction product either as such or dissolved in a suitable solvent, such as naphtha with a solution of the basic agent. As an alternative method the reaction product can be treated with solid alkaline compounds, such as KOH, NaOH, NazCOs, KzCOa, NazS, and the like, at an elevated temperature of from 100 F. to about 600 F.

The additive mixture can contain from about 2% to about preferably from about 10% to about 50%, of the metal salt of the dihydrocarbon dithiophosphate, e. g., zinc diamyl dithiophosphate, and from about 20% to about 98%, preferably from about 50% to about of the alkali metal-containing neutralized reaction product of the phosphorus sulfide and hydrocarbon. Usually the additive mixture is employed in admixture with a hydrocarbon lubricating oil to give a composition containing from about 0.1% to about 10% of the metal dihydrocarbon dithiophosphate, and from about 0.1% to about 10% of the neutralized phosphorus sulfide-hydrocarbon reaction product.

The treatment of additive mixtures of the above-described type to improve the compatibility thereof and obtain stable compositions is illustrated by the following examples:

Example I flocculent precipitate while the samples removed above 300 F. remained clear.

Example II Oils of the same composition as in Example I were heated for 2 hours With stirring at F., 200 F. and 250 F. The sample heated at 250 F. remained clear while those heated at 160 F. and 200 F. developed a precipitate.

Example III A sample of the same composition as in Example I waes heated very rapidly (about 5 minutes) with stirring to 360 F. and then allowed to cool. The sample de- Veloped a precipitate.

Example IV Three additive concentrates were prepared, each containing 69.5% of the KGB neutralized reaction product of P285 and a polybutene of about 1000 molecular weight and 30.5% of zinc diamyl dithiophosphate. These samples were then stirred for 2 hours, one at 225 F., one at 250 F., and one at 300 F. Oil solutions were then made up to contain 3.3% of the heated concentrate samples and 96.7% of a solvent-extracted 20 grade oil. These oil solutions of the heated additive concentrate were heated and stirred at 140-l60 F. for 20 minutes and then cooled. The additive mixture heated at 225 F. formed a precipitate in the oil while the samples heated at 250 F. and 300 F. remained clear.

The oil vehicle can be any natural or synthetic hydrocarbon lubricating -oil of suitable viscosity, usually within the range of from about 50 seconds at 100 F. to about 110 seconds at 210 F. Saybolt Universal. The oil may be unextracted or extracted with any of the well-known solvents and/or otherwise treated by any of the Wellknown refining processes.

The percentages given herein and in the appended claims are weight percentages unless otherwise stated.

I claim:

1. The method of preparing a stable compatible composition comprising in admixture a hydrocarbon lubricating oil, from about 20% to about 98% of an oil-soluble reaction product of a phosphorus sulfide and a hydrocarbon, neutralized with an alkali metal basic compounds, and from about 2% to about 80% of a polyvalent metal salt of a dihydrocarbon dithiophosphate normally unstable 6 in said composition, comprising heating said admixture at a temperature of from about 240 F. to about 450 F. for at least one-half hour until a cooled sample of the heat-treated mixture remains clear without developing a precipitate after about at least 3 weeks.

2. The method of preparing a stable compatible composition comprising in admixture a hydrocarbon lubricating oil, from about 20% to about 98% of an oil-soluble reaction product of a phosphorus sulfide and an olefin polymer neutralized with an alkali metal basic compound, and from about 2% to about of a zinc salt of a dialkyl dithiophosphate normally unstable in said composition, comprising heating said admixture at a temperature of from about 240 F. to about 450 F. for from about 6 hours to about one-half hour, respectively.

3. The method of preparing a stable lubricant composition comprising a hydrocarbon lubricating oil, from about 0.1% to about 10% of a reaction product of phosphorus pentasulfide and a polybutene of about 1000 molecular weight neutralized with a basic potassium compound and from 0.1% to about 10% of zinc diamyl dithiophosphate which normally precipitates out of said lubricant composition, comprising heating said lubricant composi tion to a temperature above about 250 F. for at least one-half hour until a cooled sample of the beat-treated product will not form a precipitate.

References Cited in the file of this patent UNITED STATES PATENTS 2,476,813 Buckmann July 19, 1949 

1. THE METHOD OF PREPARING A STABLE COMPATIBLE COMPOSITION COMPRISING IN ADMIXTURE A HYDROCARBON LUBRICATING OIL, FROM ABOUT 20% TO ABOUT 98% OF AN OIL-SOLUBLE REACTION PRODUCT OF A PHOSPHORUS SULFIDE AND A HYDROCARBON, NEUTRALIZED WITH AN ALKALI METAL BASIC COMPOUNDS, AND FROM ABOUT 2% TO ABOUT 80% OF A POLYVALENT METAL SALT OF A DIHYDROCARBON DITHIOPHOSPHATE NORMALLY UNSTABLE IN SAID COMPOSITION, COMPRISING HEATING SAID ADMIXTURE AT A TEMPERATURE OF FROM ABOUT 240*F. TO ABOUT 450F. FOR AT LEAST ONE-HALF HOUR UNTIL A COOLED SAMPLE OF THE HEAT-TREATED MIXTURE REMAINS CLEAR WITHOUT DEVELOPING A PRECIPITATE AFTER ABOUT AT LEAST 3 WEEKS. 